With a conventional fuel injection device (described in British Patent Application No. 2 281 101), a fuel vaporizer has a vaporizer chamber into which fuel is injected by an injection valve through an inlet orifice. When an ordinary glow plug that is arranged in the vaporizer chamber is heated, it causes the fuel to evaporate. The fuel vapor formed in the vaporizer chamber can escape through a small nozzle into the intake area of a downstream combustion chamber together with air entering the vaporizer chamber through a corresponding air inlet.
When the glow plug is deactivated after the warm-up phase after a cold start, fuel is discharged through the vaporizer chamber only due to the internal combustion engine intake air flowing through the vaporizer chamber, with the small nozzle causing the fuel to be atomized.
With another conventional fuel injection device (described in German Patent Application No. 28 43 534), a heating element-with vaporizer surfaces is provided upstream from the spray orifice in the fuel discharge area of an injection valve on the intake side, so that the fuel to be vaporized is sprayed onto the vaporizer surfaces of the heating element. A vaporizer area defined by the heating element is open on the outlet side. With this convential fuel injection device, a heating element with a honeycomb structure that is likewise open on the outlet side may also be provided to improve the heat transfer to the fuel.
If such a heating element in the spray area of the injection valve is not heated, it presents a relatively large obstacle for the sprayed stream of fuel and interferes with fuel processing to produce the mixture.
Therefore, with conventional fuel vaporizers arranged in the spray area of an injection valve, problems occur in processing the mixture, i.e., in processing the fuel to produce the fuel-air mixture when the fuel vaporizer is not heated electrically during continuous operation of the internal combustion engine, because the fuel vaporizer has a negative effect on the fuel stream produced by the injection valve and thus interferes with fuel delivery.
Another conventional fuel injection device described in German Patent No. 20 57 972 includes injection valves that are assigned to the individual combustion chambers of an internal combustion engine and receive fuel through pipelines from a fuel metering device. The fuel thus supplied enters a valve chamber of the respective injection valve that is closed by an outlet valve on the outlet end. The outlet valve includes a valve body that is preloaded in its closed position by a spring and is opened by the fuel pressure in the valve chamber when the force exerted by the fuel on the valve body exceeds the closing force of the spring.
Each injection valve has a heating body in its interior with which the fuel in the injection valve can be heated so that it evaporates even when the engine is cold, namely when it flows out through the outlet valve and expands in the outlet area of the injection valve.